class Student():
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __str__(self):
        return f'{self.name} is {self.age} years old'

    def __lt__(self, other):
        return self.age < other.age

    def hi(self):
        print(f'大家好，我是{self.name},今年{self.age}')


p = Student('aj', '17')
stu = Student('周杰伦', '18')
stu.hi()
print(stu)
print(stu.age>p.age)
print(stu.age<p.age)